EyeWorld Asia-Pacific September 2014 Issue

54 EWAP rEfrActivE September 2014 Toric IOL selection with and without intraoperative aberrometry by Ellen Stodola EyeWorld Staff Writer Comparing the two in a practice I ntraoperative aberrometry can help a surgeon in determining factors such as spherical power, toric power, and alignment power. It is particularly helpful in cases that are more complicated than a standard cataract procedure, like those with higher degrees of toric power, higher astigmatism, and post- LASIK cases. In a presentation at the 2013 American Academy of Ophthalmology meeting, Kathryn Hatch, MD , Talamo Hatch Laser Eye Consultants, Waltham, Mass., U.S., and assistant clinical professor, Warren Alpert Medical School of Brown University, Providence, RI, U.S., discussed toric IOL selection and positioning with and without the use of intraoperative aberrometry. “Intraoperative aberrometry gives us real-time aphakic and pseudophakic readings and can assist with IOL choice, including both toric and spherical power calculation, as well as assist with astigmatism management with LRIs and toric IOL alignment,” Dr. Hatch said. She referenced a study she worked on to determine the value of intraoperative aberrometry in cases of toric IOL implantation. The study was a non-randomized, retrospective, comparative trial in a private practice setting with two surgeons, Dr. Hatch said. In the aberrometry group, cylinder power and axis of Views from Asia-Pacific Abhay R. VAsAVAdA, Ms, FRCs (England) Director Vaishali VAsAVAdA, Ms Consultant Iladevi Cataract & IOL Research Centre Raghudeep Eye Clinic, Gurukul Road, Memnagar, Ahmedabad – 380 052, India Tel. no. +91-79-27490909 vaishali@raghudeepeyeclinic.com T oday, IOL outcomes define cataract surgery outcomes. Surgeons and industry alike are striving towards the common goal of hitting targeted postoperative refraction. Intraoperative aberrometry promises to give real-time refraction during cataract surgery in the aphakic and pseudophakic eye. Provided these systems are found to be reliable, repeatable, and user-friendly, they will help in refining precision to a previously unachieved level. This would hold true for both spherical power as well as astigmatic magnitude and axis. Currently, two systems are available for clinical use: the ORA® by Wavetec vison and the Holos intraoperative aberrometry by Clarity. Both of these are mountableon the operating microscope. Although they work on different principles, they provide aphakic and pseudophakic refraction. As the article reports, when the ORA system was used to align the toric IOLs as compared to the conventional system of using biometry data and an online toric IOL calculator, there was a greater reduction in the postoperative residual astigmatism in the ORA group. Currently, toric IOL power and axis determination is based on some form of preoperative corneal curvature measurements. Intraoperative alignment is based on a reference mark created before surgery, or using iris registration to identify and mark the axis, or using automated software registration, e.g. Verion (Alcon Laboratories, Fort Worth, Texas, U.S.). We personally feel that having the ability to check the refraction of the eye and then be able to make adjustments in toric IOL placement, or even change the spherical power will make premium IOL practice not only more precise but maybe even more user-friendly. This technology is the first of its kind to be able to give input intraoperatively based on aphakic refraction as to what spherical power, how much astigmatic power and at what axis IOL needs to be aligned. Not only is this helpful in toric IOL patients, but also in other IOLs such as monofocals or multifocals, it can guide the surgeon in performing LRIs, AKs or other touchup procedures to manage co-existing astigmatism. Also, as is being widely discussed in literature, posterior corneal curvature does play a role, often significant in the corneal astigmatism. Although technologies like the Scheimpflug imaging (Pentacam), Galilei, Orbscan also incorporate posterior corneal curvature in their measurements, using aphakic refraction data will help to negotiate even this factor when planning the IOL. Further, with its newer upgrade, the Verrify, the ORA system indicates when the refraction becomes stable, and when it is unstable so that the surgeon can implant only based on a stable refraction reading. Intraoperative aberrometry also is projected to be more useful in complex IOL calculation scenarios such as post- refractive surgery, or high degrees of ametropia/astigmatism. However, this technology is still evolving and many more developments are still to be expected. The readings may be affected by pressure from the lid speculum, squeezing movements, hypotony or overfill of the chamber. The stability of intraoperative refraction and the effect of wound healing on the final refractive outcome are also limitations with this technology. While this technology relies on intraoperative readings to decide IOL power and placement, the stability of this refraction is not yet known. Further, wound healing and modulation is another factor that will lead to changes in the final postoperative refraction. Therefore, unlike the light adjustable IOL technology, this technology is useful only for making adjustments during surgery All in all, intraoperative aberrometry seems to be one step forward in being able to give reproducible and bang-on target refractions time after time. Editors’ note: Neither of the doctors has any financial interests related to their comments.